The 2012 vote will be closely watched by both campaigns, partisan and nonpartisan monitors, and thousands of lawyers prepared to go to court over irregularities.

Peg Rosenfield has been monitoring elections for the League of Women Voters in Ohio for almost 40 years and has seen just about every voting glitch imaginable. She says there's a saying among election workers:

"Please, God, make it a landslide."

In a landslide, there is no quibbling over hanging chads or provisional ballots or registration requirements or rigged voting machines or whether ballots were cast by the dead. A winner is declared, a loser concedes — election over.

No one expects a landslide when Americans go to the polls on Tuesday. As in 2000 and 2004, there is great potential for the race to be too close to call immediately in some states, and the possibility that the presidency will hang for days or weeks on a recount, or on the counting of provisional or late-arriving absentee ballots.

It is possible the election won't be decided at the polls alone, but, as in 2000, that it will determined in court — or in Congress.

"The best chance is that we end up with a winner declared on election day and then everything's done," said Rick Hasen, an election law specialist at the UC Irvine School of Law, but "there is no question that there will be some glitches on election day." The question is how serious they are and whether they will decide the winner.

This much is known: The election will be subjected to unprecedented scrutiny by both campaigns, by a variety of partisan and nonpartisan monitors, and by thousands of lawyers prepared to go to court at the sight of the slightest irregularity.

"It's the new normal," said Ed Foley, an election law expert at Ohio State University's Moritz College of Law. "You could see some lawsuits that may end up not amounting to much, but skirmishes as the candidates try to control the terrain."

Much more is not known:

• Extended road closures or power outages from Sandy could make voting difficult in the hardest-hit areas. For the most part, the worst damage occurred in states that are considered safe for President Obama, but snow in the southwestern mountains of Virginia — an important battleground state — could disrupt voting in districts where Mitt Romney is strongly favored.

The storm has already disrupted early voting, which could put more pressure on precincts on election day, or keep some people from voting altogether.

• In some states, the outcome could hinge on provisional ballots, the validity of which was uncertain when they were cast. In Ohio, where more than 200,000 provisional ballots were cast in 2008, state law requires a 10-day waiting period before they can be counted. With polls showing the presidential race to be very close in the state, it isn't hard to imagine a scenario in which an electoral college majority hangs on the results in Ohio, but no winner can be determined until Nov. 17.

• In the battleground states of Colorado and Florida, a recount is mandatory if the margin between the candidates is within 0.5% of the total vote. In Ohio, it is mandatory if the margin is within 0.25%.

How likely is such a close finish? Not so unlikely. In 2004, the margin between George W. Bush and John F. Kerry was within 0.4% in Wisconsin. In 2000, the vote between Bush and Al Gore was within 0.01% — one one-hundredth of 1% — in Florida, where a recount was ultimately stopped by the U.S. Supreme Court. It was also within half a percentage point in five states, including Ohio, and under a quarter of a percentage point in two of those states.

• Members of both parties seem convinced that the other side has tricks up its sleeve.

On the right, the tea party-affiliated group True the Vote has geared up for election monitoring aimed at preventing voters from casting fraudulent votes, while groups on the left and center have mobilized to ensure that no one is improperly stopped from voting.

True the Vote founder Catherine Engelbrecht said in an e-mail interview that her group had no plans to disrupt voting or intimidate anyone.

"True the Vote trains citizen poll watchers to never communicate verbally or nonverbally with voters — they are not even allowed to offer directions to a restroom or give the time of day!" she said. There have been complaints in the past about the group's behavior at the polls, and there have been reports this year that True the Vote volunteers had been hired as poll workers in some Ohio precincts.

While most studies have shown that instances of individuals casting fraudulent ballots are extremely rare, Engelbrecht said the threat remains high, especially through the unauthorized use of absentee ballots.

"To date we've referred 99 cases of potential interstate voter fraud to authorities in Florida, New York, Ohio and Rhode Island," she said. "We've subsequently learned that Florida and Rhode Island have begun criminal investigation processes." Those involved two people suspected of casting votes in both states in a past election, authorities said.